Late Middle English; earliest use found in Reginald Pecock (c1392–?1459), bishop of Chichester and religious author. From over- + highly, after over-high.
Definition of over-highly in US English:
over-highly
adverbˌəʊvəˈhʌɪli
Too highly; extremely highly.
Origin
Late Middle English; earliest use found in Reginald Pecock (c1392–?1459), bishop of Chichester and religious author. From over- + highly, after over-high.